Al2O3/Cu复合材料的高温拉伸性能研究

Al2O3弥散强化铜基复合材料(Al2O3/Cu复合材料)因其具有优良的高强度高导电性能以及抗高温软化性能而成为备受瞩目的一种工程材料.本文研究了Al2O3/Cu复合材料的室温和高温拉伸性能及微观组织.研究表明该材料相比Cu-Cr合金(Cr0.7%wt)具有优越的高温强度.微观组织观察表明该材料高温下优越的强度主要是因为弥散而细小的Al2O3颗粒的存在阻碍了位错运动,抑制了晶粒长大和Cu基体的再结晶.动态回复和局部再结晶是主要的软化机制.断裂特征表现为局部韧性断裂.)     

不同浓度Cu-Al2O3弥散强化铜合金退火行为的研究

通过力学性能测试和金相观察对中、低浓度Cu-Al2O3弥散强化铜合金的退火行为进行了研究.结果表明低浓度弥散强化铜合金具有一定的抗高温软化性能,500℃退火后发生再结晶,900℃退火后已基本完全再结晶,屈强比约为56%.中浓度合金抗高温软化性能较好,900℃退火后,合金仍然以回复过程为主,金相尺度下不能看到再结晶晶粒,屈强比可达70%.弥散强化铜合金优越的抗高温软化性能归功于铜基体内均匀弥散分布有纳米Al2O3粒子.     

Al2O3/Cu复合材料强化机理研究

采用内氧化法制备了Al2O3／Cu复合材料，进行了高温电子拉伸实验，并通过微观组织观察，分析了该复合材料的强化机理。拉伸实验结果显示：Al2O3／Cu复合材料不仅室温强度很高，而且高温时仍保持较高的强度。微观组织观察分析表明：细小的Al2O3颗粒的弥散分布是该复合材料具有高强度的主要原因，表现在：Al2O3颗粒存在能够抑制Cu基再结晶的进行；Al2O3颗粒的存在阻碍晶界亚晶界运动，从而阻碍晶粒长大；Al2O3颗粒的阻碍位错运动，增加位错密度；Al2O3颗粒的存在提高材料的蠕变抗力。     

Al2O3弥散强化铜基复合材料的制备及物理性能的研究

采用硝酸盐分解法制备Al2O3弥散强化铜基复合材料,通过测试材料的硬度、抗软化温度和电导率,研究了Al2O3增强相对材料性能的影响。结果表明,Al2O3颗粒弥散分布在铜基体上,制备的Al2O3弥散强化铜基复合材料的强度、硬度、软化温度等远高于纯铜,具有良好的高温性能,当Al2O3含量为1．0％时,复合材料的软化温度在800℃以上、硬度达到125HB。     

纳米Al2O3p/CU复合材料的再结晶微观结构分析

针对传统高导电材料的抗软化温度较低的不足，研究开发了高软化温度的纳米Al2O2颗粒增强Cu基复合材料。测试了Al2O3p／Cu复合材料的退火温度-硬度关系曲线，采用扫描电子显微镜、透射电子显微镜和能谱仪分析了其再结晶过程的微观组织结构变化规律。结果表明，Al2O3p／Cu复合材料具有很高的再结晶软化抗力，退火温度超过900℃再结晶过程才明显进行；其晶粒直径在0．5～5μm之间，α—Al2O3质点直径在10～20nm之间，且主要分布在亚晶界上；探讨了Al2O3p／Cu复合材料再结晶形核机制和纳米氧化铝质点对再结晶核心长大的影响。     

高浓度氧化铝弥散强化铜合金的高温力学行为（英文）

研究Cu-2.7%Al2O3弥散强化铜合金的微观组织及其高温力学行为。结果表明:细小的Al2O3粒子均匀分布在铜基体当中,部分粗大的Al2O3粒子分布在晶界上。拉伸试验表明Hall-Petch机制是影响氧化铝弥散强化铜合金室温屈服强度的主要因素,其高温强度主要由于Al2O3粒子对晶界和亚晶界与位错的强烈钉扎作用。合金在700°C下的抗拉强度和屈服强度分别达到237 MPa和226 MPa。拉伸断口表明弥散强化铜合金显示出高温脆性。蠕变测试表明400°C下的稳态蠕变速率比700°C下的稳态蠕变速率小很多,其400°C和700°C的蠕变应力指数分别为7和5,蠕变机制为位错核心扩散型和晶格扩散型蠕变。     

内氧化法制备Al2O3/Cu复合材料的再结晶

利用内氧化法制备了Al2O3/Cu复合材料,研究了该材料在不同冷拔变形量和Al2O3含量下,其硬度值随退火温度变化的规律,并进行了显微组织结构分析。结果表明:采用内氧化法制备的Al2O3/Cu复合材料,在铜基体中弥散分布着纳米级的Al2O3颗粒;经900℃×1h退火后,其硬度可保持室温的87%以上;其再结晶温度高达1000℃;变形量和Al2O3含量增加均使硬度提高,但对软化和再结晶温度影响不大。     

20%Mo/Cu-Al2O3复合材料的强化机理及热变形行为

采用真空热压-内氧化烧结方法制备20%Mo/Cu-Al2O3复合材料,测试其性能并观察分析其微观组织。利用Gleeble-1500D热力模拟试验机在温度为350~750℃、应变速率为0.01~5 s-1及总应变量0.5的条件下,对20%Mo/Cu-Al2O3复合材料热变形过程中的流变应力与应变之间的关系进行研究。结果表明:20%Mo/Cu-Al2O3复合材料的组织分布均匀,未观察到明显的团聚现象及孔洞,致密度较高。在材料基体上,原位内氧化生成的纳米级Al2O3颗粒呈弥散分布,增加了基体的强度。复合材料的高温流动应力—应变曲线以动态再结晶软化机制为主,峰值应力随变形温度的降低或应变速率的升高而增加;在真应力—真应变曲线基础上建立的高温变形本构方程较好地表征了此复合材料的高温流变特性,其计算结果与实验结果吻合较好。     

内氧化法制备Al2O3/Cu点焊电极的装机试验

采用内氧化法制备了0．6Al2O3／Cu复合材料，以该复合材料棒材为原料制备了点焊电极，并进行了装机试验和微观组织结构分析。研究结果表明：采用内氧化法制备的0．6Al2O3／Cu复合材料在铜基体中弥散分布着纳米级细小Al2O3颗粒。由于Al2O3颗粒硬度高，热稳定性和化学稳定性好，使该复合材料制备的点焊电极抗塑性变形能力强、抗坑蚀能力优良、再结晶温度高，并具有优越的抗粘接能力，使用寿命是铬锆铜电极的3倍多。     

氧化物弥散强化的钼

美国CSM工业公司可提供高温性能优良的氧化物弥散强化(ODS)的钼材,包括薄板、厚板、圆棒和方棒。氧化物弥散强化的钼,大约含有2Vol%La2O3细粒分布在显微组织中。这些氧化镧颗粒稳定了材料的晶粒结构,提高了抗再结晶能力,高温强度高于钼或TZM合金。当这种材料确实发生再结晶时,氧化镧颗粒就促使其生成特别能抗蠕变的细长、联锁晶粒结构。CSM工业公司所用的弥散氧化物颗粒的方法是材料获得优良性能的关键,它不同于这种材料的其它生产者所采用的技术。抗再结晶能力是很重要的,因为它使材料在使用过程中保持高的强度,最终的结果是…     

A new constitutive equation for strain hardening and softening of fcc metals during severe plastic deformation

The stress–strain relationship for strain hardening and softening of high-purity aluminum and copper, which were deformed by equal channel angular pressing (ECAP) at ambient temperature, was analyzed by combining the Estrin and Mecking (EM) model and an Avrami-type equation with experimental data during severe plastic deformation. The initial strain hardening can be described by the EM model, while the flow stress arrives at the peak stress after it was saturated. However, strain softening similar to plastic deformation at high temperatures is observed after the peak stress. Moreover, the peak strain at the maximum flow stress is ∼4 for copper and ∼2 for aluminum. A new constitutive equation was developed to describe strain softening at high strain levels, which was supported well by tensile, compression and microhardness tests at room temperature and low strain rate. It was observed that dynamic recovery and recrystallization occurs in copper, and recrystallized grains and their growth in aluminum. The results indicate that dynamic recovery and recrystallization was the dominant softening mechanism, which was confirmed by scanning electron microscopy–electron channeling contrast observations and the abnormal relationship between the imposed strain during ECAP and subsequent recrystallization temperature after ECAP.     

Simulation of strain-softening behaviors in an AZ31 Mg alloy showing distinct twin-induced reorientation before a peak stress

To investigate strain-softening behavior during plastic deformation of an AZ31 Mg alloy, cylindrical specimens were compressed in a rolling direction at 300 °C. Experimental evidence revealed that an inhomogeneous microstructure evolved due to the softening behavior associated with deformation at elevated temperatures. The large grains that reoriented as a result of deformation twinning were free of dynamic recrystallization (DRX). Fine grains nucleated at grain boundaries of grains were deformed by a slip-dominated mechanism, which accommodated the external strain. A visco-plastic self-consistent (VPSC) polycrystal model was used to simulate softening of the flow stress curve and texture evolution during uniaxial compression. A softening scheme was implemented in the polycrystal model to predict the softening phenomenon and texture evolution after the peak stress. The original VPSC model was modified to simulate texture evolution in an AZ31 Mg alloy that exhibited twin-dominated deformation before the peak stress.     

6016铝合金热变形实验模拟热轧显微组织演变(英文)

采用Gleeble-1500热模拟机研究6016铝合金单道次高温压缩变形时的显微组织演变。采用光学显微镜和透射电子显微镜分析合金在不同变形条件下的组织形貌特征。结果表明:在高温压缩变形时,该合金的变形激活能为270.257kJ/mol,硬化指数为8.5254;流变应力双曲正弦的自然对数值与温度补偿Zener-Hollomon参数自然对数值成线性关系;合金低温、低应变速率时的主要变形组织为动态回复组织,而高温变形时产生局部动态再结晶组织;该铝合金高温变形时的主要软化机制为动态回复,只有在高温、高应变速率下发生部分的动态再结晶;合金平均亚晶粒尺寸随温度补偿应变速率Zener-Hollomon参数的升高而减小。     

Deformation behavior of Mg–Zn–Y alloys reinforced by icosahedral quasicrystalline particles

New Mg-rich Mg–Zn–Y alloys, reinforced by quasicrystalline particles, have been developed by thermomechanical processes. The deformation behavior of these alloys at room and elevated temperatures has been investigated. Yield strength of these alloys, which increases with an increase in the volume fraction of quasicrystalline particles, is relatively high due to their strengthening effect. The variation of the flow stress in the alloys is characterized by linking the microstructural evolution during deformation at high temperatures. The flow softening is related to dynamic recrystallization developed under the dislocation climb controlled creep; the flow hardening is related to grain growth that occurs under the grain boundary diffusion controlled creep. Quasicrystalline particles in the Mg–Zn–Y alloys resist coarsening due to their low interfacial energy, thereby forming of stable quasicrystalline particle/matrix interface and also prohibit against microstructural evolution of the α-Mg matrix during deformation at temperatures up to near the eutectic temperature. Stability of both quasicrystalline particles and matrix microstructure in the Mg–Zn–Y alloys provides large elongation to failure with no void formation at the quasicrystalline particle/matrix interface.     

热变形参数对新型Al-Zn-Mg-Cu高强铝合金微观组织的影响

采用Gleeble-1500D热力模拟试验机进行新型Al-Zn-Mg-Cu高强铝合金的热压缩实验,变形程度为10%～80%,变形温度为300℃～450℃,应变速率为0.001s-1～10s-1。利用光学显微镜(OM)和透射显微镜(TEM)观察合金在不同压缩条件下的组织形貌特征,分析了热变形参数对微观组织的影响。研究结果表明,试验温度范围内,变形程度达到50%以上时,试样呈锻态变形组织,且变形程度的增大,有利于动态再结晶的进行;随着变形温度的升高和应变速率的减小,位错密度减小,亚晶粒尺寸增大。新型Al-Zn-Mg-Cu合金热压缩变形过程中主要的软化机制为动态回复和动态再结晶,当应变速率为0.01s-1、变形温度为300℃～400℃时,主要发生动态回复;当变形温度为450℃、应变速率在0.001s-1～10s-1范围内时,其变形以动态再结晶为主。     

T2纯铜线性摩擦焊接研究

采用不同摩擦压力进行T2纯铜线性摩擦焊接工艺试验。接头组织性能测试发现,焊缝为经历了再结晶的细小晶粒,局部存在漩涡状流线、未焊合孔洞及夹杂缺陷,热力影响区仅发生回复,与母材组织接近,焊缝及热力影响区整体较宽;当摩擦压力提高到50 MPa及70 MPa时,抗拉强度接近母材平均值。分析表明,T2纯铜塑性好、导热快,焊接过程接头易形成较宽的软化区,使界面金属塑性流动变差,导致缺陷产生,应考虑提高热输入速度予以改善。     

Deformation behavior of dispersion-strengthened copper at high temperature

1. Introduction Dispersion-strengthened copper (DSC) is a promising material developed recently. Considerable attention has been focused on it because of its excel- lent high-temperature properties. The metallic mate- rial, which is strengthened by solution strengthening, deformation strengthening, and ageing strengthening, is always low at high temperature, and the strength- ening factor contradicts with the electrical conduc- tivity of the material to a certain extent [1-2]. But DSC has g…     

退火温度对铝青铜微观组织及硬度的影响

利用光学显微镜、扫描电镜、XRD和硬度计等分析了Cu-Al-Ni合金在冷轧与退火过程中微观组织结构及硬度的变化规律,研究了合金在不同退火温度条件下的软化行为。结果表明,当采用950 ℃保温淬火工艺后,Cu-Al-Ni合金主要由面心立方结构的α相与体心立方结构的β相组成,分布于晶界处的β相对合金硬度的影响作用小。由于位错强化作用的显著增强,合金在冷轧后硬度明显升高,达到270 HV0.5。冷轧态Cu-Al-Ni合金在400 ℃以上温度退火后会发生明显软化现象,软化的主要原因是再结晶反应所引起的位错密度下降。Cu-Al-Ni合金的再结晶温度在300 ℃以上,高于纯铜的再结晶温度,这表明Ni、Al元素的添加有利于提高纯铜再结晶温度,并能改善其高温抗软化性能。     

紫铜-黄铜搅拌摩擦焊接头的组织与力学性能

研究了紫铜和黄铜搅拌摩擦焊接的可行性,对焊接接头的金相组织进行了分析,并通过拉伸实验、硬度分析、弯曲实验,对接头的性能进行了验证.结果表明:紫铜-黄铜具有良好的搅拌摩擦焊接性能,可获得与母材等强度的搅拌摩擦焊接接头.焊合区在热力偶合作用下获得动态再结晶组织,接头黄铜一侧热影响区沿厚度方向上下不同,下侧可分为再结晶区、不完全再结晶区、动态回复区;上侧出现明显的偏析现象;接头紫铜一侧热影响区出现明显的须状组织,并有晶粒微溶的迹象.